Charging Issues,

Does this '63 Dart have the original wiring and charging system? If you do not know, please post some pix of the regulator and the back of the alternator.

If this is charging that hard and is the original '63 system, it likely has a bad/wrong regulator or is miswired. There is a blue wire that carries 12v to the regulator. If all is well, at fast idle, a low voltage of a few volts will be measured out of the other regulator terminal onto the green wire that goes to the single field wire to the back of the alternator. Check the voltage on this green wire: anything near to 12v on this on the original '63 system will cause the alternator to produce an overcharge.

If you have a later alternator system, then we need to know as it will behave differently.